Detector tube



Aug. 28, 1923. 1,465,998

H. C. RENTSCHLER DETECTOR TUBE Filed Feb. 27, 1919 20 2b 21 WITNESSES: Screen Paige/ma] 'INVENTOR Harvey C fieflfsc/z/er ATTORNEY Patented Aug. 28,

l were; STATES. i

insane earner oral-ion.-

I HARVEY C. RENTSCEILER, 01F WILKINSBURG, PENNSYLVANIA, ASSIGN'QR T WEST- KNGHEQUSE LAMP C'OBIIPANY, A CORPQRATION OF PENNSYLVANIA.

DETECTOR TUBE.

Application filed February 27, rain. Serial no. araeea.

To all whom it may concern:

Be it known that I, HARVEY C. RENT- SCHLER, a citizen of the United States, and a resident of Wilkinsburg in the county of Allegheny and State'of ennsylvania, have invented a new anduseful Improvement in Detector Tubes, of which the following is a specification.

system embodying a tube constructed in accordance with my invention Fig. 2 is a diagram illustrating the various operating characteristics obtainable with the' tube of Fig. 1; and Fig. 3 is a sectional view of atube illustrating the phenomenon of resonance.

In the operation of a detector bulb, the i11 Zooming impulses are applied. as'a modulating force to control the current strength in a local circuit, and it is desirable that the percentage change in the modulated current be as pronounced as possible, in order to detect extremely weak signals. I find that, by mounting a hot cathode, a plate anode and an intervening screen in a tube containing argon or other, suitable gas or vapor and by the maintenance of the screen at a higher potential than either of the remaining electrodes, said operation may be secured in ac cordance with the following principles, the controlling electr'omotive force being connected to modulate the potential of the screen with respect to the cathode and the local current flowing in a circuit including the plate electrode and thescreena .As the potential of the screen, with respect to the cathode, is raised, the velocity 90f the electrons traveling from the cathode to the anode is gradually raised and the electrons, therefore, reachthe anode at a constantly increasing velocity and are either reflected therefi'om or cause the emission of secondary electrons therefrom, this action being initiated at difierent veloclties' with difi'erent materials for the plate electrode.

The rebounding'electrons; or the secondary electrons travel back toward the, screen under the influence of two forces, namely, that derived from the impacting energy and that established by the fact that the screen is positive with respect to-the plate electrode. As the electron velocity is raised higher-and higher, these reflected or secondary electrons eventually reach the screen and tend to initiate current flow from the screen to the plate electrode in opposition to the normal current flow which is from the plate electrode, causing a dip in the characteristic obtained by plotting plate current against grid potential.

7 As the velocity is raised still higher, -the effect of the main electron stream overpow:

ers that of the reflected stream, and the characteristic curve again begins to, rise.

Thus, a ronounced hump or maximum point is produced in the characteristic curve and, byadjusting for operation at this point, a relatively strong modulation'of the,

local current, with a relatively weak incoming signal, maybe secured.

'Furthermore,. the tube being filled with argon gas or some'other suitable material exhibiting the phenomenon of resonance, there may be produced a characteristic curve having a series-of maximum and minimum points, all asfully explained in my copending application, filed February 27, 1919, Serial No. 279,581, electron tube apparatus, and assigned to the WestinghouseLamp Company. By proper .adg'yustment ofthttube, a maximum point due to re a ance; may be made to coincide with the maximise point due to electron refiectionor secondary emission and thus a verypron'ounced maximum point may be'obtained for extremely sensitive operation. Referring to the, drawing for a rnore detailed understanding of my invention, show a receiving antenna at 5, connected t ground at 6 through the primary winding of a coupling transformer 8 having a secondary member 9. A tube 10 is provided for detector purposes having a plate electrode 11, a filamentary cathode 12 and an intervening screen'electrode' or grid 13.

- The filamentary cathode 12 may be maintained at incandescence, as by a battery 14, for supplying electrons to the interior of the container T e screen electrode 13 is the screen 13 and, as hitherto pointed out,

these electrons travel under'the' joint inmaintained positive with respect to the cathode 12, as by an adjustable battery 15 and, similarly, the screen electrode 13 is maintained positive with respect to the plate electrode 11, as by an adjustable battery 16 of lesser voltage than the battery 15.

The secondary winding 9 is connected between the cathode 12 and the screen electrode 13 through battery 15, and a receiving device 17 is connected in circuit with the cathode 12, windingtl, batteries 15 and 16 and the plate electrode 11.

Tn the operation of the device thus described, the batteries 15 and 16tend to maintain a fixed difierence of potential between the respective electrodes, and the efiect of incoming impulses through the secondary winding 9 is to vary the potential of the screen and plate with respect to the cathode 12. v

As the potential of the screen 13, with respect to the cathode 12, is raised, as by increasing the efl'ective voltage of the battery 15, the plate current or the current circulating from the plate 11 through the tube and the battery 16,'gradi1ally increases because of the greater number or electrons drawn out from the cathode -12 by the electrostatic attraction'of the screen .20-.-21 in the curve 20-22 of Fig. 2.

13. This efl'ect may be plotted as a line 0 With the gradually increasing screen potential, the electron velocity is correspond- I 36 ingly increased until, at a critical velocity,

dependent upon the nature of the electrode 11, electron reflection or the generationQf secondary electrons by bombardment is initiated at the surface of the electrode 11 so that electrons move back therefrom toward fluence of the energy of rebound and of-th'e electrostatic attraction'because (if the fact action of the screen potential, theelectrons eventually reach the screen in appreciable numbers, establishing current flow from the screen 13 to the plate 11 down through the' receiving apparatus 17 and the-battery 16 back to the screen 13, in opposition to the main local current flow which is from the electrode 11 to the electrode 12, thence The effect of this reverse-current flow is to temporarily reduce the current flowing through the receiving device '17, as indicated by the portion 21-23 of the characteristic curve 20-22.

As the potential of the screen electrode is still furtherincreased, the-main electron stream overpowers this reverse electron stream, and the current through the device 17 again starts to increase, as indicated by the portion 23-22 of the characteristic curve 2022.'

In the normal use ot'the device, theadjustment is such that functioning is obtained at the maximum point 21 or at the minimum point 23 The modulating efiect of the alless than the value 27-21, resulting in a marked variation of the current through the receiving apparatus.

Up to this pomt, the action of the bulb 10 has been somewhat the same as though highly evacuated so that substantially pure electron emission would be involved but if, as disclosed andpreferred, the tube be filled with argon.- ga's, operation in accordance with the phenomenon of resonance is 'secured, as fully set forth in my copending application above referred to. Briefly stated, this action, is as: follows:

an electron upon a molecule of argon gas is elastic, that is. to say, the electron bounds o'fi withsubstantially no abstraction of ener- .Under normal conditions, the impact of n and without aflecting the gas molecule. certain critical velocities, .however, ap-

pare ntly bearing some critical relation to th electron velocity within the molecules,

this action is'radially modified and the im-v pact becomes highly non-elastic, the energy 'of the impacting electron being materially reduced.

Two types of inelastic impacts between electrons and atoms in certain monatomic gases and vapors have been found to exist. The first occurs when'the' colliding electron displaces an electron of the atom without removing-it from'the atom. That is, it moves an electron from one orbit to another in the same atom. The phenomenon of electronic displacement in the atomic system without removal of an electron is called resonance.

velocity, corresponding to non-elastic impact, to cause resonance at a point suchas 40 ad acent to the screen. The escaping electron has relatively low velocity and is,

therefqleitaken y the screen 13, thus.

producing a marked diminution in the number of electrons reaching the plate 11, as compared with the number that reached this plate when the electron velocity was so low that the electrons did not suffer non-elastic impact until after passing through the screen 13. j

As the potential of the screen 13 is raised, the acceleration imparted to the electrons is also increased, so that the critical velocity corresponding to non-elastic impact is attained at a point, such as 41,'some distance from the screen. The escaping electron, whether primary or secondary in nature, receives such acceleration from the screen before reaching the same as to, in most cases, p ss therethrough and impact upon the plate electrode, thus materially increasing the plate current. 1 r

As the screen potential is still further "increased, the critical velocity corresponding to non-elastic impact is attained at some such point as 42, and the escaping electron again 7,

attains thiscritical velocity at a point, as 43, adjacent to the screen. The resultant escaping electron is taken up, in most cases, by the screen and thus, the plate current is again diminished.-

This cyclical change in the plate current continues indefinitely, with increasing screen potential until terminated by other non-per tinent phenomena.

Thus, by filling a tube 10 with argon gas and by gradually increasing the "velocity of the electrons by increasing the screen po-- tential, a characteristic curve 20-30 .may be secured having maximum points 31'-32 33, where non-elastic imp-act is "initiated near the screen and having minimum points 34 and 35 where non-elastic impact adjacent the screen is discontinued.

By suitable adjustment of the electrode spacing and of the relative potentials therebetween, the maximum point 31 of'the characteristic curve 20 30'm'ay be made to occur at the same grid potential as the maximum point 21-onthe curve 2022, producing. a very marked maximum. point 36 onthe 'resultant or net characteristic curve 2037 of the entire device. By operating 'at this pronounced maximum point 36, an extremely' sensitive device is secured. V

, While I have described my invention in its preferred form, it will be obvious to those'skilled in the art that it is not so limited but issusceptible .of various changes and modifications withoutdeparting from the spirit thereof and I desire, therefore, that only such limitations shall. be placed thereupon as are imposed by the prior art or are specifically set forth in the appended claims.

I 'claim as my invention:

1. In an electron-tube system, the combination with a tube provided with an electron-emittingcathode, an anode and an intervening conducting screen in a medium exhibiting the phenomenon of resonance, of

means for maintaining said anode positive with respect to said cathode, means for maintaining said screen positive wlth respect to each of the remaining electrodes,

said last-named means being so adjusted that the plate current is at a maximum or a minimum value because of theoefl'ect of electron reflection or secondary emissionof said screen with respect to v for maintaining said screen positive with respect to each of the remaining electrodes and for maintaining said anode positive with respect to said cathode, whereby the may be represented by a curve having ,a definite maximum and a definite minimum point, a filling of gas within said tube exhibiting the phenomenon of resonance, whereby the characteristic maybe represented by a-c'urve exhibiting a pluralit of maximum and minimum points, the ad ustment being such that a critical point of one characteristic curve coincides in screen poscreen potential, plate-current characteristic tentialwith a similar critical point of the other characteristic curve, and means for modulating the screen potential about said value. i

3. Ina three-electrode, electron-tube systerm, the combination with means for prdducing a situation which may be re resented by a plate-current, screen-potentia characteristic curve having a point where the slope changes sign and dependent upon electron reflection or the production of secondary electrons, said means also serving to produce a situation which may be represented by a plate-current, screen-potential characteristic curve'having a point where the slope changes sign because of resonance, said two points occurring at a similar screen-potential, and means for modulating the screen potential about said point.

4. The combination with a three-element tube comprising a cathode, grid and anode arranged in the order mentioned in a medium exhibiting the phenomenon o f res'onance, of means for maintaining the grid at a positive potential with respect to both the anode and the cathode, means for impressing a controlling potential upon the grid, and means for utilizing the resultant current flowing in the anode, the constants being so adjusted that electron refleetion or secondary-emission efi'ects are produced in said anode of such nature as to produce a change in the sign of the slope of the curve plotted between anode current' and rid potential.

. 5. he combination with a three-element tubecomprising a cathode, grid and anode arranged, in the order mentioned, in a medium exhibiting the phenoinenon of resonance, of means for maintaining the grid at a positive potential with respect to both the anode and the cathode, means for impressing a controlling potential upon the grid, and means for utilizing the resultant current flowing in the anode; the material of the anode, the distances between electrodes, the grid potential, the intervening medium and the pressure being so chosen that the irregularities, due to secondary emission or reflection from the anode, in the curve plotted between anode-current and grid potential, substantially correspond with similar irregularities due to the resonance phenomenon.

6. The method of operating an electron tube including a cathode, an anode and an intervening screen electrode in a medium exhibiting the phenomenon of resonance;

reeaeee l Inodulatin I 7. The method of operating an electron tube including a cathode, an anode and an intervening screen electrode in a medium exhibiting the phenomenon of resonance; comprising maintaining the screen electrode more positive than the anode, adjusting the potentials applied to the tube sothat, because of electron reflections or secondary emission from the anode, the characteristic curve, plotted to' show the relation between the plate current and the potentials-ofthe screen, changes sign, and modulating the screen potential at such a point, whereby great sensitivity is obtained.

8. The method of operating an electron tube including a cathode, an anode and an intervening screen electrode enclosed 'in a medium exhibiting the phenomenon of res onance; comprising adjusting the impressed potentials, sothat the eflects of electron refiection or secondary emission from the anode and resonance in the medium, are

cumulative, so-that the maximum points of the separate characteristics, represented as plate-current, screen-potential curves, correspond at adefinite screen' potential, and such screen potential to obtain great sensitivity in using the tube as a detector.

lin testimony whereof I have hereunto subscribed i'ny name this 24th day of Feb, 11.919.

HARVEY e. RENTSCHLER: 

